1. No, self harm is not ok.
2. Who says the living of lives does not repeat over time? Your/our "next" life may start in 300 B.C.
Two things science knows barely something about: consciousness and the arrow of time. The self is only an illusion. Physics has lots of symmetry. Therefore, it would make sense if the universe was fair in the end. So the egg theory actually makes sense, more sense than anything else I've heard actually.